In deep sea drilling operations, huge quantities of drill cuttings can accumulate around a drilling rig. A growing awareness of the environmental impact of these drill cuttings has resulted in regulations requiring their removal and treatment. However these drill cuttings tend to agglomerate and are difficult to remove quickly and efficiently. The inventors have devised a method of fluidising settled solids, in order to cause the solids to form a slurry which can be removed from the sea bed for treatment, storage or transport. In order to improve the efficiency of the process, it has been proposed that once the drill cuttings have been fluidised, they are transported to shore or into a vessel in a continuous or batch process, so that the rate at which the drill cuttings can be removed is maximised.
In an alternative application, it may be desirable to drain a tank containing for example toxic and/or radio active waste with both liquid and solid constituents. For example it may be that the original storage tank has corroded, or the contents are to be removed for treatment. In this application, it is clearly important that the contents of the tank are contained at all times and that the volume of material which is transferred is minimised while still providing sufficient disturbance of the solids in the tank to ensure complete suspension of the solids and controlled emptying of the tank. Alternatively, it may be desirable to remove the solids/sludge from the bottom of the tank, without overly disturbing the fine solids, and in particular without adding to or subtracting from the volume of liquid in the tank, thus ensuring that the required liquid level in the tank is maintained. This has particular relevance when the liquid level above the solids acts as a radiation shield.